The present invention relates to a drum winder including winding drums that support a roll that is being formed, i.e., onto which a web is being wound, and which is provided with a cutter device for cutting the web after the roll has reached a desired size and before the web begins to wind onto a new empty roll spool. The cutter device comprises a cutter blade, an actuator, and power transmission means operationally connected to the cutter blade of the cutter device so that the movement of the actuator is transferable by means of the power transmission means to the cutter blade. In this manner, the cutter blade moves along a curved path of movement so that the position of the cutter blade in the lower position is substantially more distant from the winding drum than it is in the upper position.
The present invention also relates to a method for winding a web onto a roll in a drum winder in which the web is supported on winding drums and a gap formed between the winding drums and the roll is pressurized.
In drum winding, it is desirable to lower the linear nip loads produced by the weight of the growing roll, because otherwise the linear loads that act in the nips will become excessively high, causing defects in the roll.
With respect to the prior art, reference is made to the publications DE 1,047,001, DE 1,111,496, DE 3,618,955, and U.S. Pat. No. 3,497,151. In the devices described in these prior art references, it is known to pass a pressure into the gap formed by the roll that is being formed and by the winding drums, whereby a relief effect is applied to the roll that is formed. As a result of this effect, the linear loads in the nips cannot become excessively high. In order that the pressure should be retained in the gap formed by the roll and by the winding drums, it is known from the prior art to seal the gap from above and from below, respectively, by means of various sealing constructions. From the publication DE 1,047,001, it is known to move the upper roll-end sealing unit in an axial direction of the roll.
In addition, from U.S. Pat. No. 3,346,209, it is known to regulate the pressure present in the gap formed by the roll and the winding drums by moving the lower drum in a substantially vertical direction, i.e., up and down.
Even though by means of the prior art devices described above, considerable improvement in the winding of a web onto a roll is achieved, they involve certain drawbacks. For example, sealing of the gap formed by the roll that is formed and the winding drums is generally problematic. The pressure always leaks to some extent, which results in problems of dust formation. Owing to the leakage of the pressure, a very large quantity of air is needed to maintain the pressure, which air spreads into the working environment, for which reason the dust is readily separated from the web that is wound and spreads into the working environment.
Moreover, the prior art devices restrict or at least hamper some operations that are necessary in the roll formation. One of these operations is the roll change wherein when the roll that is being wound becomes complete, a new roll spool must be fed into the gap between the winding drums, the web that is wound must be cut off, and the end of the cut-off web must be attached to the new roll spool. Thus, during roll change operations, various actuators are needed, such as web holders, cutting means, devices for the feed of a new roll spool, etc.
In the assignee's Finnish Patent Application No. 902890 of earlier date (corresponding to the assignee's U.S. patent application Serial No. 07/713,137, the specification of which is incorporated by reference herein), a cutter device is described for a web winder. The cutter device comprises a frame construction and a cutter blade for cutting the web in the roll formed on support of the winding drums before a new winding is started onto an empty roll spool. The cutter device comprises an actuator and power transmission members operatively connected to the cutter blade of the cutter device so that the movement of the actuator is transferable by means of the power transfer members to the cutter blade. In this arrangement, the cutter blade is movable along a curved path of movement so that the position of the cutter blade in its lower position is substantially more distant from the carrier drum than in its upper position. If necessary, such a cutter device may be connected with a blower device for holding the cut-off web end, a web holder, and/or a threading member for the web being wound onto the new, empty roll spool. The cutter blade of the cutter device moves along a curved path of movement into the gap between the winding drums, for example, from below the gap.
By means of a cutter device described in FI Pat. Appl. 902890, an advantage is obtained in that it is not necessary to make any installation pit for the frame construction of the cutter device, e.g., in the floor of the production plant. The cutter device can be attached to the frame of any drum winder whatsoever. In addition, it is easy to attach other accessories to the cutter device that are necessary for carrying out the roll change operation. Such accessories include, for example, the above blower for holding the cut-off web end, the web holder, and the threading device, etc.